Changes in rheological and low-temperature characteristics of rubberized asphalt containing castor-based bio-oil under thermal-oxidative exposure

The proposed bio-modified rubberized asphalt (BMRA) technology integrates bio-oil and crumb rubber modifications, offering cost savings, waste reuse, improved asphalt performance, and reduced asphalt consumption. Like traditional asphalt, BMRA ages over time due to external environmental factors, impacting its pavement performance. This study examines the alterations in rheological and low-temperature characteristics of BMRA during thermal-oxidative aging. Results indicate that incorporating bio-oil minimizes alterations to the complex modulus and phase angle in aged asphalt. BMRA's crossover modulus significantly surpasses that of unaged rubberized asphalt (RA), showcasing the mitigating effect of bio-oil and crumb rubber on asphalt's rheological properties during aging. BMRA demonstrates comparable or enhanced peak load, fracture displacement, fracture toughness, and fracture energy relative to RA. BMRA's glass transition temperature remains lower than that of other unaged asphalts, signifying enhanced resistance to low-temperature cracking even after aging. Bio-oil, characterized by low molecular weight and abundant light components, counteracts performance deterioration attributed to volatile constituents and destabilization of asphalt's colloid structure during aging. Crumb rubber facilitates the absorption and subsequent release of specific light components, augmenting BMRA's resistance to aging. These findings enhance our understanding of the mechanisms governing the aging resistance and performance of bio-modified rubberized asphalt, thereby supporting the development of sustainable and durable asphalt materials.